Various substituted pyridines, such as the nicotinic acid derivatives, are essential to the living organisms. The phosphorus analog of pyridine, phosphabenzene, is very similar to pyridine. It is proposed to synthesize corresponding derivatives of phosphabenzene to some of the biologically active pyridines so that they can be tested for activity. It will be necessary to develop new general methods of synthesis of 2, 3 and 4-substituted phosphabenzenes.